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Use a shared email account and simply save drafts of your messages without sending them. The other person can log in, read, and respond.

Of course, Petraeus was found out, so let’s look at some alternatives.

Black SMS

This iPhone app turns your secret messages into scrambled nonsense pictures that you can pass along via text message. The recipient loads the images into the app, which converts them back to normal text.

Want to tell your boss what you really think? Use Silent Sender to anonymously email him or anyone else from right inside your Web browser. (Don’t use your work computer, though—employers have ways of tracking this kind of activity on corporate networks.)

When you send a text message through the usual means, you relinquish control of it. Wickr is an app that lets you maintain control and remove your messages from the recipient’s phone. You can even use a self-destruct option.